Common rail fuel injectors spend only a small fraction of their operational time actually injecting fuel, and a vast majority of the remaining time standing by in a pressurized state ready for a subsequent injection event. In many cases, a pressurized area within the fuel injector can be separated from a low pressure area by a guide surface of a movable valve member. Because pressure differentials between the pressurized area and the low pressure area can be relatively high, the pressure gradient tends to cause fuel to migrate up through the guide area to the low pressure region, and this migration of fuel can account for a majority of fuel leakage from a fuel injector. As fuel injection pressures continue to rise, this type of fuel leakage problem can correspondingly become more acute. In addition, as common rail fuel injection systems are scaled for larger and larger engines, the associated fuel injectors can be expected to have larger clearance areas for their larger internal components. Thus, in high pressure common rail systems associated with large bore fuel systems, the fuel leakage along guide surfaces can become unacceptable. Simply scaling up proven solutions from smaller bore fuel injection systems to larger bore fuel injection systems can also be problematic. First, the physics with regard to fluid dynamics, mass properties and pressures, etc. do not scale well. And even if they did scale, the larger bore fuel systems must then necessarily have different components thereby increasing the parts catalog count for an engine manufacturer that manufactures both small and large bore fuel systems and associated engines.
The present disclosure is directed toward one or more of the problems set forth above.